This happened when the monster, who was wielding a weapon, got hit
by a disintegration blast, and then lifesaved by a worn amulet.
if (otmp->owornmask) {
/* in case monster's life gets saved */
mon->misc_worn_check &= ~otmp->owornmask;
+ if (otmp->owornmask & W_WEP)
+ setmnotwielded(mon, otmp);
/* also dismounts hero if this object is steed's saddle */
update_mon_intrinsics(mon, otmp, FALSE, TRUE);
otmp->owornmask = 0L;